1. Field of the Invention
This specification relates to a delay time generation apparatus for an air circuit breaker, and more particularly, a delay time generation apparatus for an air circuit breaker capable of improving reliability for a generation of a delay time in the air circuit breaker.
2. Background of the Invention
In general, a circuit breaker refers to an apparatus that opens and closes a load in a power system, a distribution system or an electric circuit and cuts off a current when an accident such as grounding or short-circuit occurs.
Some of such circuit breakers are provided with a relay executing a so-called making current release (MCR) function of setting a current value, detecting an introduced current and instantaneously blocking an introduction of a heavy current over the set current value, so as to prevent the introduction of the heavy current into a load side.
In order for the relay to execute the MCR function, a case of opening the circuit breaker for blocking a fault current (i.e., separating a fixed contactor and a movable contactor from each other) in a closed state of the circuit breaker should be distinguished from a case of blocking a fault current upon closing the circuit breaker (i.e., contacting the movable contactor contact with the fixed contactor) on a circuit which is already open due to an occurrence of a fault.
To distinguish the two cases, a delay time generation apparatus for a circuit breaker is used for outputting a contact signal (or conductive signal) with a predetermine delay time after the movable contactor is brought into contact with the fixed contactor.
Meanwhile, FIG. 1 is a schematic view illustrating a delay time generation apparatus for a circuit breaker according to the related art.
As illustrated in FIG. 1, the related art delay time generation apparatus includes a switch 20 disposed at one side of a main shaft 10 to output a signal upon detecting a contact state, a delay plate 30 rotatably disposed to be contactable with or separated from the switch 20, and a lever 12 integrally formed with the main shaft 10 to press the delay plate 30 upon a rotation of the main shaft 10 in a breaking direction, such that the delay plate 30 is rotated away from the switch 20.
The delay plate 30 includes a rotation shaft 31, a first arm 33 extending from the rotation shaft 31 toward the main shaft 10 and contactable with the lever 12, and a second arm 35 extending from the rotation shaft 31 toward the switch 20 and rotated simultaneously with the first arm 33 to be contactable with the switch 20.
In this instance, the second arm 35 is connected with a spring 37 that supplies an elastic force in a direction that the second arm 35 comes in contact with the switch 20.
Also, the second arm 35 is provided with a mass body 39 causing a predetermined delay time due to inertia upon a rotation of the main shaft 10 in a closing direction.
With the configuration, in a broke state of the circuit breaker, when the main shaft 10 is rotated in the closing direction, the delay plate 30 is rotated toward the switch 20 in a clockwise direction by the elastic force of the spring 37. In this instance, a predetermined delay time is generated during the rotation of the delay plate 30 due to the inertia of the mass body 39. The delay time is generated in response to the delay plate 30 being brought into contact with the switch 20 after the fixed contactor and the movable contactor are brought into contact with each other due to the rotation of the main shaft 10.
However, the related art delay time generation apparatus uses a large mass body, the apparatus increases in size which makes it difficult to install the generation apparatus in a narrow space.
Also, the generation of the delay time using the mass body brings about lowered accuracy of the delay time and difficulty in ensuring a sufficient delay time.